Spark plug



Nov. 16, 1943. H. K. KING SPARK PLUG Filed Nov. 27, 1941 IN V ENTORPatented Nov. 16, 1943 UNITED STATES PATENT OFFICE SPARK PLUG Henry K.King, Bethesda, Md. v ApplicationNovember 27,1941, Serial No. 420,625

19Claims. (o1. res-169) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) My invention relates in generalto spark plugs and has particular reference to'spark plugs utilizing aseries of spark gaps as distinguished from the more conventional plughaving only a single gap.

It has long been common practice to manufacture different types ofplugs'for different fields of application. These can be divided ingeneral in v to two classes. tively low temperatures require a hot plug,i. e., a plug designed to operate at a high temperature to prevent oildeposit thereon which otherwise would tend ot cause the plug to misiire,commonly referred to as fouling. n the other hand, engines which operateat relatively high temperatures require a cold plug, 1. e., a plugdesigned to operate at a low'temperature to prevent preignition whichotherwise would tend to cause the plugto fire ahead of time.

In modern high powered combustion engines,

such'as for example those used onaircraft, it has long been a problem todesign a spark plug which will give satisfactory performance throughoutextremes in operating temperature conditions of the engine. When theengine is operating at'full power, its temperature is of course at amaximum and hence there is a tendency towards preignition of the plug,but when the engine is operating at minimum power its temperature isobviously also at a minimum and thus there is a tendency towardsfouling.

It is therefore a broad object of my invention Engines which operate atrela-- to provide an improved spark plug for acombustion engine whichwill maintain a substantially uniform temperature and thereby'rendersatisfactory service throughout extremes in operating temperatures ofthe engine.

A specific object of my invention is to provide a spark plug having gapsin series in which I the base member forming the outer electrode isspaced from the outermost intermediate electrode to form a chambertherebetween to permit entry tailed description ac's theattached draw-With respect to the drawingin which like reference numerals indicatelike parts;

Fig. 1 is a vertical section of a spark plug illustrating a preferredembodiment of my inven tion, and

Fig. 2 is abotto mplan view of the plug shown m Fig. 1.

With reference now in particular to 1, my

improved spark plug contains an inner or central metallic electrode 1which is taperedslightly and cylindrical in contour; The'uppe'r portionof electrode I is made hollow so that this sec-.- tion will-have arelatively low heat conducting. capacity. This feature. of constructionprevents overheating of the top of the plug which other wise might causedamage ,to the high voltage lead (not illustrated) which is attached tothe top of electrode l in any well known manner.

- Surrounding electrode I are a plurality of sleeves 3 and 5 made of anygood conductive metal which form intermediate electrodes. These sleevesare also tapered to the contour of the centralelectrode and areelectrically separated from each other and from the central electrode bymeans of tapered sleeves 2 and 4 which may be made from any suitablenon-conductor such as, for example, sheet mica, and preformed to size ifdesired. 4

Insulating sleeves 2 and 4 may extend for substantially the entirelength of the central electrode l to increasethe gas sealing qualitiesof the plug. Intermediate sleeve electrodes 3 and 5 terminate, however,at substantially the juncture between the hollow and solid portions ofthe central electrode. To fill the'space above these intermediateelectrodes,iinsulating sleeves l and 8, also tapered and preformed ifdesired,'are positioned between insulating sleeves 2 and 4, and 4 and 8respectively.

An annular metallic member 9 having a frus'toconical shouldered portionI0 is provided for holding the alternately arranged electrode sleevesand insulating sleeves firmly in position with respect to the centralelectrode. Being tapered, the sleeves will of course be heating.

A shell H is provided for receiving the electrodes and contains an upperfemale threaded cylindrical portion 12 for receiving a cylindricalshielding member I3. A.lower male threaded tightened further upon and anoutwardly flared portion formed on the central electrode I.

I'he lower cylindrical screw portion H of shell H receives the assemblyof electrode and insulating sleeves and is spaced from the outer surface of electrode sleeve by the particular construction of member 9 andinsulatingjsleeve 6 to form a gas chamber 22 therebetween. The bot- "tom'of portion I4 is turned inwardly. at v23 as 4 shown to form a gasnozzle 24 whereby the gases of combustion which .enter the chamber uponthe compression stroke of the engine may be su b sequently dr'awnoutwardly from .the' chamber with'a' high'velocity to render the gapselfcleaning.

' The hot gases circulating in chamber 22 also maintain the outersurface of electrode 5 at an elevatd temperature which is suflicient. toprevent fouling between this electrode and the inner wall of the lowerportion M- of shell ll.

=It will -be noted that the intermediate sleeve electrodes 3 and{terminate at substantially the juncture between the hollow andsolidportions of'el'ectrode I, which juncture is formed substant-iallyatthetop of member 9 By providing a ;"coristruc'tion of thistype, thatportion of the plug above-the intermediate electrodes 3 and 6 will ha'vea-relatively lowheat' conductivity with f theresult that the greaterpart of the heat in the plug which will riserapidly from .the' sparkarea because of the highly conductive heat path prog videdbythe'metallic electrodes 3 and-5 and solid electrode 5 will be ;drivenoutwardly therefrom substantially a transverse'direction across arelatively high conductive heat path comprising member 9,'shell II andgasket H to theengine 7 block l5. This rapid dissipation of heatgenerated is effective to prevent local overheating of the electrodes inthe area adjacent the-spark high temperatureoperating conditions.

' *The'operation of my improved plug is as follows: High voltage issupplied in any well known manner as from a spark coil, one side ofwhich temperatures; paratively low, the plug will not .foul between isgrounded, through a suitably insulated conducto'r to the-top of thecentralelectrode I. .Since one side of the spark coil'isgrounded, as isalso the engine block 15, an arc will be formed between the centralelectrode 1 and electrode 3 from whence it will jump to electrode andthen to-b'ase portion [4.

Becapitulating, it will be evident that the structure which hasbeendescribed"- is a distinctive and meritorious advance in the art in thatit'pro- -vides' a spark plug which-will render'satisfactory operationover extreme differentials in operating When thewtemp'erature is com- 1"theouter electrode and intermediate electrode, "particularly-at theupper part of the chamber '22, where fouling is mostlikely to occur;-the gas action into and'out of chamber 22 across ,noz "zle"2'4-' rendersthe plugself-cleaning; and the highly conductive heat path furnished bythe central and intermediate electrode assembly serves to prevent localoverheating of the electrodes in the area adjacent the spark gap whenthe operating temperature is high to thereby minimize possibilities forpreignition.

In conclusion, it will be evident to those skilled in the art thatvarious changes may be made in "the form, details of'construction andarrangement of parts herein described without departing from the spiritand scope of my invention. I therefore desire it to be understood thatonly such limitations as are imposed by the prior art shall be placedupon the appended claims.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

' Having now fully described my invention, what .I claim is:

1. In a spark plug utilizing spark discharge .4 between a plurality ofgaps in series, the combination comprising an inner electrode, at leastone sleeve of conductive material constituting an intermediateelectrode, the bottom edge of said conductive sleeve forming an annuluscoplanar with the bottom edge of said inner electrode, means forinsulating said inner and intermediate electrodes from each other, and ahollow base portion forming an outer electrode, the inner' wall of saidbase portion being spaced fromthe exterior surface of the outermostintermediate electrode to form a chamber therebetween.

2. The combination of claim'l wherein the chamber has a reducedcross-sectional area at the spark path between the intermediateelectrode and the outer electrode to form a gas nozzle. I

, 3. In a spark plug utilizing spark discharge between a plurality ofgaps in series, the combination comprising an inner electrode, at leastone annular sleeve of conductive material ar- ""pathand will thereby'prevent preignition under ranged coaxially therewith and forming anintermediate electrode, an annular sleeve of nonconductive material forinsulating said inner and intermediate electrodes from each other, and atubular male threaded base portion disposed coaxiallywith saidelectrodes forming the outer electrode, the inner wall of said baseportion being spaced from the exterior surface of the outermostintermediate electrode to form a gas ,chamber therebetween for renderingthe spark gap self-cleaning, said chamber having a, relatively smallarea adjacent the spark path and a substantially greater areathereabove.

4. In a spark plug utilizing spark discharge between a plurality of gapsin series, the combination comprising an inner electrode, a plurality ofannular sleeves of conductive material forming intermediate electrodes,sleeves of non-conductive material for insulating the inner electrodefrom the intermediate electrode nearest thereto and for insulating theintermediate electrodes from each other and a tubular base memberforming the outer electrode, said base surrounding said inner andintermediate electrode assembly and being spaced therefrom to form a gaschamber between the inner wall of said base and the exterior surface ofthe outermost inter- -media'te electrode.

5. The combination of claim 4 characterized by the fact that thecross-sectional area of the chamber at thespark path between theoutermost intermediate electrode and theouter electrode is reduced toform a gas nozzle.

6. In a spark plug utilizing spark discharge between a plurality ofgaps, the combination comprising a tapered inner electrode, a pluralityof tapered conductive sleeves disposed coaxially with said innerelectrode and formingintermediate electrodes, said intermediateelectrodes being arranged to provide a spark path thereacross normal tothe longitudinal axis of said inner electrode, insulating means forelectrically separating the inner electrode from the intermediateelectrode nearest thereto and for electrically separating theintermediate electrodes from each other, and a tube like body memberforming the outer electrode, said bodymember being disposed coaxiallywith said inner and intermediate electrodes and spaced therefrom to forma gas chamber between the inner wall of said body member and theexterior surface of the outermost intermediate electrode.

7. The combination of claim (i-wherein the cross-sectional area of thegas chamber at the spark path between the intermediate and outerelectrode is reduced to form a gas nozzle.

8. In a spark plug utilizing spark discharge between a plurality ofgaps, the combination comprising a tapered central electrode, aplurality of annular conductive sleeves of frusto-conical contourdisposed co-axially with said central electrode and forming intermediateelectrodes, sleeves of insulating material for separating the sleeves ofconductive material surrounding said 1,1 In a spark plug, thecombination comprising a tubular male threaded bas member for screwinsertion into a gas chamber and serving as an outer electrode, atapered central electrode, intermediate electrodes comprising tapered ofsaid central and intermediate electrodes projecting downwardly into saidbase member and,

terminating co-planar with the bottom thereof to formseries spark gapsbetween central and.

outer electrodes, and an annular gas chamber the sides ofwhich areformed by the inner surcentral electrode from the intermediate electrodenearest thereto and the intermediate electrodes from each other, and atubular base member forming the outerelectrode, said base member beingdisposed coaxially with said central and intermediate electrodes andspaced therefromto form the side walls of a gas chamber between theinner wall of said base member and the exterior surface of the outermostintermediate electrode, the inner diameter of said base member adjacentthe spark path being such as to form a nozzle for gas entry into saidchamber.

9. In a spark plug, the combination comprising a tubular base member forinsertion into a gas explosion chamber and serving as an outerelectrode, a central electrode, at least one'sleeve of conductivematerial forming an intermediate electrode, said central andintermediate electrodes projecting downwardly into said base member andterminating co-planar adjacent the bottom of said base member to formseries spark gaps thereacross, insulating means for electricallyseparating the central from the intermediate electrodes, and a gaschamber formed by the inner surface of said base member and the outersurface of the outermost intermediate electrode.

10. In a spark plug, the combination comprising a tubular male threadedbase member for screw-insertion into a gas explosion chamber and servingas an outer electrode, an inner electrode, at least one sleeve ofconductive material face of said base memberand the outer surface of theoutermost intermediate electrode, theyinner diameter of said base memberadjacent the spark path being restricted to form a nozzle for gas entryinto saidchamber.

12. In a spark plugutilizing a spark discharge between a plurality ofgaps'in series, the combination comprising a central electrode, saidel'e'c 'trode having a lower solid portion and-an upper hollow portion,at least one sleeve of conductivematerial forming an intermediateelectrode, said intermediateelectrode being terminated at substantiallythe juncture of the solid and hollow portions of said inner electrode, abase portion forming the outer-electrode and means for insulating saidelectrodes relative to each other.

1:3. In aspark plug utilizinga spark discharge betweena pluralityof gapsinseries, the combmationcomprising a centralelectrode, saidelectrodehaving lower solid and upper hollow por tions, at least one sleeve ofconductive material forming an intermediate electrode, means forinsulating said intermediate electrode from said inner electrode, said.inner and intermediate electrodes being tapered and having their basesof larger diameter projecting downwardly into said base member andterminating co-planar with the bottom edge of said base member to formseries spark gaps thereacross and a gas chamber formed by theinner-surface of said base member and the outer'surface of the outermostintermediate electrode, the inner diameter of said base member adjacentthe spark path being restricted vmediate and outer electrodes is reducedto arranged coaxially with said central electrode to form anintermediate electrode, said conductive sleeve being terminated atsubstantially the juncture between-the solid and hollow portions of saidcentral electrode, aninsulatingsleeve disposed between said electrodesand a base portion forming the-outer electrode into which the lowerportions of said central and intermediate electrodes are projected toform a series of gaps therebetween, the inner surface of said baseportion being spaced from the exterior surface of theoutermostintermediate electrode to form a gas chamber therebetween torender the plug self-cleaning.

14. In a spark plu the combination comprising a base member forinsertion into a gas exiplosio'n'c'hamber' and serving asan outerelectrode, a central electrode having a lower solid portionand an upperhollow portion, at least one intermediate electrode, the top of saidintermediate electrode being terminatedsubstantiaHy adjacent thejuncture-between thesolid andhol-v lowportions of said central electrodeand the bottom thereoi-beingterminated co-planar with the. bottom ofsaid base member to form, a series ,of spark gaps-between said central"and outer electrodes, means for-insulatin said central and each of saidintermediate electrodes from one another, and separator means includingan insulating'member for spacing theinner surface ofsaid base memberfrom the exterior surface .oi said outermost intermediate electrode toform a chamber at the spark path betweensaid-interform 9. gasnozzle.

g to form a nozzle for gas entry into said chamber.

-16. In a spark plug the combinationcomprising a base member forinsertion into a gas explosion chamber and serving as an outerelectrode, a tapered central electrode, said electrode being hollowabove the primary path of heat flow away therefrom and solid therebelow,at least one tapered sleeve of conductive material arranged coaxiallywith'said central electrodeto form an intermediate electrode, the. topend of "-said sleevebeix'ig terminated at substantiall the jun'cturebetween the solid and hollow portions of-said central electrode andthe-bottom end thereof being terminated co-planar with. the bot- -tomend of said base member to forma series of -spark gaps, non-conductivemeans for insulating said central and each of said intermediateelectrodes from one another for substantially their entire-lengths and:separator meansincluding a non-conductive member for spacing the innersurface of said base member from the exterior -surface of said outermostintermediate electrode to "form a gas chamber therebetween. wherebysaid-plug is rendered self-cleaning ing a base member for insertion intoa gas explosion chamber and serving as an outer electrode', a taperedcentral electrode, said electrode being hollow above the primary path ofheat flow away therefrom and solid therebelow, at least one taperedsleeve of conductive material arranged coaxially with said centralelectrode to form an intermediate electrode, the top end of said sleevebeing terminated at substantially the juncture between the solid andhollow portions of said central electrode and the bottom end thereofbeing terminated co-planar with the bottom end of said base member toform a series of spark gaps, non-conductive sleeves for insulating saidcentral and each of said intermediate electrodes from one another forsubstantially their entire lengths and separator means including anon-conductive V sleeve for spacing the inner surface of said basemember from the exterior surfaceof said outermost intermediate electrodeto form a gas chamber therebetween whereby said plug is renderedself-cleaning. 4

19. The combination of claim 18 characterized by the fact that thetransverse sectional area of said chamber at the spark path between saidintermediate and outer electrodes is reduced to form a gas nozzle.

HENRY K. KING.

